ON BIOLOGICAL ANALOGIES. 277 



tively easy experiments, imitations (as near as differences of texture 

 will allow) of the most constant constituents of inflammation in 

 animals, especially those of the least acute of the productive inter- 

 stitial inflammations, leading to thickening, opacity, induration, and 

 other such changes." 



The succeeding remarks on galls and their analogues cannot be 

 abstracted, but should be read in extenso. " There are," he says, 

 " reasons enough for regarding all these galls and gall-like pro- 

 ducts of disease, generated in plants by insects, as analogous with a 

 large group of the products of inflammation, which we study in 

 our own pathology, and the analogy is not the less because neither 

 group can be circumscribed with any exact definition." Of tumours 

 he says — " The growths in plants which may, I think, be deemed 

 most nearly like to our tumours, are those which are called exos- 

 toses, knours, or wens. In many of these conditions there is a very 

 strong resemblance between these growths and some of the bony ex- 

 ostoses after which they are named. Especially when one breaks them 

 off the trunk of the beech, or the holly, or cedar, and sees their pedicle 

 of attachment and the bark-like integument and periosteum, con- 

 tinued over them, one cannot but compare them with the narrow- 

 based ivory exostoses of the skull or the pedicled exostoses which 

 are common on the femur and humerus, or with the sessile fibroid 

 uterine tumours." 



And again, " Now the history of these growths is very suggestive 

 to us. They are derived from buds, which remain, as Trecul says, 

 in a sort of lethargic state for several years, and then become active, 

 and form either a little branch, or a loupe, or exostosis, which in its 

 increase will project more and more beneath the bark. Surely they 

 may thus confirm that theory of tumours, which regards those whose 

 structure does not widely differ from the natural structures, as 

 growths derived from portions of germinal substance remaining, 

 though one knows not why, for years ' lethargic ' and then becoming 

 active, growing in their own method, and subsisting on materials 

 derived from the living parts around them." 



The whole of the address from whence the above scattered ex- 

 tracts are derived is well worthy of careful perusal by those 

 interested in tracing the resemblances between the diseases of plants 

 and animals. But we must pass on hurriedly to some other relation- 

 ships between the phenomena of disease in plants and animals not 

 included in the address to which we have alluded. 



No one would attempt to deny the hereditary transmission of 



